High Early Strength Concretes with Improved Durability

Evelina Khakimova, E.I.T., GRA H. Celik Ozyildirim, Ph.D., P.E., VTRC Devin K. Harris, Ph.D., UVA

Outline •

Problem Statement

•

Stage I – High Early Strength (HES) FRCs:

•

Stage II – Very High Early Strength (VHES) FRCs:



Compressive Strength - 3,000 psi 24 hours



Compressive Strength - 3,000 psi in 10 hours



Exploratory Lab HES-FRCs Mixtures



Exploratory Lab VHES Concrete Mixtures



HES-FRCs Field Batch Mixing and Results



VHES-FRCs Lab Batch Mixing and Results



Summary



Summary

•

Analysis of Permeability of Cracked Samples

•

Preliminary Fiber Distribution Analysis

•

Conclusions and Recommendations for Future Work 2

Problem Statement Problems

Solutions

•

Cracks

•

Elimination of bridge joints

•

Leaking bridge joints

•

Low-permeability high-performance concretes

•

High permeability concrete

•

High-Early Strength Fiber Reinforced Concretes with

•

Traffic interruptions due to time

Improved Durability (tight crack widths < 0.1 mm)

consuming repairs and construction

3

Types of Used Fibers Fiber Material Diameter [microns] Length [in.] Aspect Ratio

Polyvinyl Alcohol 38 0.375 -

Polypropylene 1.9 75

Steel 900 2.36 65

4

Stage I: High Early Strength Fiber Reinforced Concretes Compressive Strength - 3,000 psi in 24 hours •

Laboratory Exploratory Mixtures Design:

  

Engineered Cementitious Composite (ECC) with Polyvinyl Alcohol (PVA) Fibers HES-FRC with Polypropylene (PP) Fibers HES-FRC with Steel (S) Fibers

Components [lb/yd3]

HES - ECC

HES-FRC w/ PP Fibers HES-FRC w/ S Fibers

Cement Type I/II

961

720

560

Class F Fly Ash

1,153

180

140

656

360

280

Total Cementitious Material

2,114

900

700

w/cm

0.31

0.40

0.40

PVA Fibers (%)

44 (2.00%)

-

-

PP Fibers (%)

-

18.4 (1.20%)

-

S Fibers (%)

-

Water

80 (0.60%)

Admixtures SRA [gal/yd3]

1.5

-

-

Accelerating Admixture [oz/cwt]

60

75

60 5

Stage I: HES-FRC •

Compressive Strength - 3,000 psi in 24 hours

Laboratory Exploratory Mixtures Results: Compressive Strength [psi] 1 Day 7 Days 28 Days First-Peak / Peak Flexural Strength [psi] 1 Day 7 Days

HES - ECC 2,830 5,510 -

HES-FRC w/ PP Fibers 3,640 5,730 6,740

HES-FRC w/ S Fibers 3,490 5,860 7,620

450 / 1,005 660 / 1,360

575 / 740 770

535 / 845 795 / 895

7 Day Flexural Results HES-FRC Lab Mixtures

8

8

7

7

6

6

5

5

Load [kips]

Load [kips]

1 Day Flexural Results HES-FRC Lab Mixtures

4 3

4 3

2

2

1

1

0

0 0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

0

0.01

0.02

0.03

Deflection [in] ECC

HES-FRC w/ S

HES-FRC w/ PP

ECC

0.04

0.05

0.06

0.07

Deflection [in] HES-FRC w/ S

0.08

0.09

0.1

HES-FRC w/ PP

6

0.11

0.12

Stage I: HES-FRC •

Compressive Strength - 3,000 psi in 24 hours

HES-FRC: Mixture Designs • Cement amount • Accelerating admixture amount • Fresh Concrete Temperature and Curing Temperature

Component (lb/yd3)

HES - ECC

HES-FRC w/ PP 15 lb/yd3

18 lb/yd3

HES-FRC w/ S HES- FRC w/ FA HES-FRC w/ SF

Cement Type I/II

961

698

723

542

628

Class F Fly Ash

1,153

183

177

140

-

-

-

-

-

50

570

333

328

233

264

Total Cem. Material

2,114

882

900

682

678

w/cm

0.27

0.38

0.36

0.34

0.39

44 (2.00%)

-

-

-

-

Polypropylene Fibers (%)

-

15 (1.0%)

18 (1.2%)

-

-

Steel Fibers (%)

-

-

80 (0.60%)

66 (0.50%)

Silica Fume Water

PVA Microfibers (%)

Accel. Admixture [oz/cwt]

15

16.5

24

25

0

SRA [gal/yd3]

1.5

-

-

-

-

Mix Temperature [° F]

79

90

91

80

95 7

Stage I: HES-FRC •

Compressive Strength - 3,000 psi in 24 hours

Sample Collection and Temperature Monitoring

8

Stage I: HES-FRC HES-ECC: Results

Age

Plant Lab Cured (Room Temp.)

Field Cured (Varying Temp.)

1 day

2,770

3,440

28 days

6,520

6,730

First-Peak / Peak flexural strength (psi)

28 days

695 /1,245

750 /1,062

Elastic modulus (106 psi)

28 days

2.43

2.59

Permeability (C)

28 days

169

129

Test

Compressive strength (psi)

7 6

Plant

5 Load [kips]

•

Compressive Strength - 3,000 psi in 24 hours

4

Field

3 2 1 0 0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Deflection [in]

9

Stage I: HES-FRC •

Compressive Strength - 3,000 psi in 24 hours

HES-FRC w/ PP Fibers: Results 15 lb/yd3

Test

Compressive strength (psi)

18 lb/yd3

Age

Field

Plant Lab

Age

Field

Plant Lab

21 hours

-

3,100

27 hours

-

3,170

24-27 hours

3,022

3,090

31 hours

3,010

3,285

28 days

5,640

6,140

28 days

5,135

5,395

First-Peak flexural strength (psi)

1 day

490

620

1 day

389

482

28 days

720

810

28 days

700

796

Elastic modulus (106 psi)

28 days

3.31

3.39

28 days

2.94

3.10

Permeability (C)

28 days

976

643

28 days

1293

933

HES-FRC w/ PP of 18 lb/yd3

7

7

6

6

5

5

Load [kips]

Load [kips]

HES-FRC w/ PP of 15 lb/yd3

4 3

4 3

2

2

1

1

0 0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Deflection [in] 1 Day

7 Days

28 Days

0.16

0.18

0.2

0 0

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 Deflection [in] 1 Day

7 Days

28 Days

10

0.2

Stage I: HES-FRC •

Compressive Strength - 3,000 psi in 24 hours

HES-FRC w/ S Fibers: Results HES-FRC w/ FA

Test

Compressive strength (psi)

HES-FRC w/ SF

Age

Field

Plant Lab

Age

Field

Plant Lab

24 hours

-

3,440

21 hours

3,430

-

31 hours

3,930

3,334

29 hours

4,020

4,080

28 days

6,440

6,790

28 days

6,600

7,100

First-Peak / Peak flexural strength (psi)

1 day

570 / 600

585 / 640

1 day

685 / 815

640

28 days

895 / 940

980 / 1270

28 days

1090

1000

Elastic modulus (106 psi)

28 days

3.63

3.85

28 days

4.32

4.42

HES-FRC w/ SF (66 lb/yd3)

7

7

6

6

5

5 Load [kips]

Load [kips]

HES-FRC w/ FA (80 lb/yd3)

4 3 2 1

4 3 2 1

0

0 0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0

0.02

0.04

0.06

Deflection [in] 1 Day

7 Days

0.08

0.1

0.12

0.14

0.16

0.18

Deflection [in] 28 Days

1 Day

7 Days

28 Days

11

0.2

Stage I: HES-FRC Length Change

Time (days)

0.02 0 0

20

40

60

80

100

120

140

-0.02 -0.04 Length Change (%)

•

Compressive Strength - 3,000 psi in 24 hours

HES-FRC w/ S and FA

-0.06 -0.08 -0.1

HES-FRC w/ S and SF HES-FRC w/ PP (1.0%)

-0.12 -0.14 -0.16

HES-FRC w/ PP (1.2%) HES - ECC

-0.18 -0.2 -0.22 -0.24

12

Stage I: HES-FRC Summary •

HES-FRCs reached 3,000 psi in about 24 hours. •

Addition of accelerating admixtures and increased fresh concrete temperatures enabled strength gain at early ages.

•

Fly Ash and Silica Fume SCMs were used to improve durability, without detriment to strength gain.

•

All concretes had low permeability.

•

All three HES-FRC systems had high cementitious content and high shrinkage values. ECC having the greatest shrinkage, followed by HES-FRC with PP and HES-FRC with S fibers.

•

Addition of fibers was beneficial to crack control.

Transition from HES 24-hour 3,000 psi concrete to VHES 10-hour 3,000 psi concrete Stage II: Very High Early Strength Fiber Reinforced Concretes Compressive Strength - 3,000 psi in 10 hours 13

Transition from HES 24-hour 3,000 psi concrete to VHES 10-hour 3,000 psi concrete  For 10-hour mixtures: •

The w/cm ratios were reduced,

•

Increased fresh concrete temperatures of 85° F - 95° F were used,

•

Higher amount of accelerating admixtures to reduce concrete setting time and increase early strength were used,

•

Insulated curing was utilized,

•

Increased cement amounts were used.

14

Stage II: VHES-FRC

Compressive Strength - 3,000 psi in 10 hours

15

Stage II: VHES-FRC •

HES 2,000 psi concretes are used in VDOT for pavement repair work

Compressive Stregth [psi]

Components [lb/yd3] Cement Type I/II Class F Fly Ash Water Fine Aggregate Coarse Aggregate w/cm Admixtures [oz/cwt] Hardening Accelerating Set Accelerating

8000

8-hour Mix 752 279 1156 1711 0.37

5-hour Mix 800 275 1129 1711 0.34

36

48 -

6000

8-hour Mix - IC

5000

5-hour Mix - IC

4000 3000

Improved 6.5-hour Mix

2000 0

20 24

Current and Improved Pavement Repair Mixtures Compressive Strength Results

7000

1000

Improved 6.5-hour Mix 750 132 265 1061 1676 0.30

5 hrs

6 hrs

7 hrs Age

8 hrs

24 hrs

IC – Insulated Curing

16

Stage II: VHES-FRC

Compressive Strength - 3,000 psi in 10 hours

•

VHES Plain Concrete Trial Mixtures for bridge structures

•

VHES w/ FA has the same mixture design as Improved modified 6.5-hour patch mixture

Components [lb/yd3]

VHES w/ SF

VHES w/ FA

Cement Type I/II

750

750

Silica Fume (6%)

50

-

-

132

Water

272

265

Total cementitious material

800

882

w/cm

0.34

0.30

Set Accelerating

24

24

Hardening Accelerating

30

20

Class F Fly Ash (15%)

Admixtures [oz/cwt]

17

•

Stage II: VHES-FRC

VHES w/ SF Trial Mixtures VHES w/ SF Compressive Strength Results

Compressive Strength [psi]

7000 6000 5000 4000 3000 2000 1000 0 6 hours

7 hours

VHES w/ SF @ 72°F

8 hours Age

MP (11 hours)

VHES w/ SF @ 84°F

24 hours

VHES w/ SF @ 90°F

Temperature Development over Time VHES w/ SF @ 72°F

VHES w/ SF @ 84°F

VHES w/ SF @ 90°F

150 140

Temperature [°F]

130 120 110 100 90 80 70 60 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Age [hours] Set Time

3,000 psi compressive strength reached

18

•

Stage II: VHES-FRC

For pavement repairs 2,000 psi compressive strength was required within 6-8 hours In our study 3,000 psi compressive strength was required within 10 hours VHES w/ FA Compressive Strength Results

Compressive Stregth [psi]

7000 6000 5000 4000 3000 2000 1000 0 6 hours

7 hours 24 hours Age VHES w/ FA @ 75°F VHES w/ FA @ 85°F

Temperature Development over Time 150 140 130 Temperature [F]

• •

VHES w/ FA Trial Mixtures

120 110 100 90 80 70 60 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Age [hours] VHES w/ FA @ 75 °F

VHES w/ FA @ 85 °F

19

Stage II: VHES-FRC •

Compressive Strength - 3,000 psi in 10 hours

VHES-FRCs with Silica Fume or Fly Ash: Lab Batch Mixture Designs

Components [lb/yd3]

VHES-FRC w/ SF

VHES-FRC w/ FA

Cement Type I/II

750

750

Silica Fume (6%)

50

-

Class F Fly Ash (15%)

132

Water

272

Total cementitious material

800

265 882

w/cm

0.34

0.30

PP Fibers (%) S Fibers (%)

15 (1.00%)

-

15 (1.00%)

-

-

80 (0.60%)

-

80 (0.60%)

Admixtures [oz/cwt] Set Accelerating Hardening Accelerating

24 20

24 20

Mix Temperature [°F]

87

96 20

Stage II: VHES-FRC

VHES-FRCs with Silica Fume or Fly Ash: Results VHES Temperature Development over Time VHES w/ SF - S VHES w/ FA - S

VHES w/ SF - PP VHES w/ FA - PP

145 140 135 130 125 Temperature [F]

•

Compressive Strength - 3,000 psi in 10 hours

120 115 110 105 100 95 90 85 80 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.5 11 11.5 12 12.5 13 Age [hours] Set Time

3,000 psi compressive strength reached

21

Stage II: VHES-FRC

VHES-FRCs with Silica Fume or Fly Ash: Results Compressive Strength Results 9000 8000 7000

Compressive Strength [psi]

•

Compressive Strength - 3,000 psi in 10 hours

6000 5000 4000 3000 2000 1000 0 6.5 hours

7.5 hours

8 hours

8.5 hours

24 hours

7 Days

28 Days

Age VHES w/ SF - S

VHES w/ SF - PP

VHES w/ FA - S

VHES w/ FA - PP

22

Stage II: VHES-FRC •

Compressive Strength - 3,000 psi in 10 hours

VHES-FRCs with Silica Fume: Results

28 Day Results

First Peak / Peak Flexural Strengths [psi]

VHES w/ SF - PP VHES w/ SF - S

1075 1100 / 1371

Residual Strength [psi] 𝒇𝒇𝑫𝑫 𝟔𝟔𝟔𝟔𝟔𝟔

428 1159

Toughness [in.-lb]

Equivalent Flexural Strength Ratio [%]

𝑻𝑻𝑫𝑫 𝟏𝟏𝟏𝟏𝟏𝟏

𝑹𝑹𝑫𝑫 𝑻𝑻,𝟏𝟏𝟏𝟏𝟏𝟏

𝒇𝒇𝑫𝑫 𝟏𝟏𝟏𝟏𝟏𝟏 642 858

233 452

Flexural Results VHES w/ SF - S

8

8

7

7

6

6

5

5

Load [kips]

Load [kips]

Flexural Results VHES w/ SF - PP

4 3 2 1

51 96

4 3 2 1

0

0 0

0.02 0.04 0.06 0.08 8.5 hours

0.1 0.12 0.14 0.16 0.18 0.2 0.22 Deflection [in] 24 hours 7 days 28 days

0

0.02 0.04 0.06 0.08 8.5 hours

0.1 0.12 0.14 0.16 0.18 Deflection [in] 24 hours 7 days

23

0.2

0.22

28 days

Stage II: VHES-FRC •

Compressive Strength - 3,000 psi in 10 hours

VHES-FRCs with Fly Ash: Results

28 Day Results

Residual Strength [psi]

First-Peak / Peak Flexural Strengths [psi]

VHES w/ FA - PP VHES w/ FA - S

1096 1116 / 1138

Toughness [in.lb]

Equivalent Flexural Strength Ratio [%]

𝑻𝑻𝑫𝑫 𝟏𝟏𝟏𝟏𝟏𝟏

𝑹𝑹𝑫𝑫 𝑻𝑻,𝟏𝟏𝟏𝟏𝟏𝟏

𝒇𝒇𝑫𝑫 𝟏𝟏𝟏𝟏𝟏𝟏

𝒇𝒇𝑫𝑫 𝟔𝟔𝟔𝟔𝟔𝟔

403 1042

568 909

216 428

Flexural Results VHES w/ FA - S

8

8

7

7

6

6

5

5

Load [kips]

Load [kips]

Flexural Results VHES w/ FA - PP

46 90

4 3 2 1

4 3 2 1

0

0 0

0.02

0.04

0.06

8.5 hours

0.08

0.1 0.12 0.14 Deflection [in]

24 hours

0.16

7 days

0.18

0.2

0.22

28 days

0

0.02

0.04

8.5 hours

0.06

0.08

0.1 0.12 0.14 0.16 Deflection [in] 24 hours 7 days

0.18

24

0.2

28 days

0.22

Stage II: VHES-FRC

Compressive Strength - 3,000 psi in 10 hours Time (days)

0.01 0.00 0

10

20

30

40

50

60

70

Length Change (%)

-0.01 -0.02 -0.03 -0.04 -0.05 -0.06 -0.07 -0.08

•

VHES-FRC w/ SF - S

VHES-FRC w/ SF - PP

VHES-FRC w/ FA - S

VHES-FRC w/ FA - PP

Shrinkage values similar to HES-FRC 24-hour mixtures due to similar cement and high paste contents 25

Stage II: VHES-FRC Summary 

All VHES-FRC mixtures reached 3,000 psi in within 10 hours • •

VHES-FRC with Silica Fume reached 3,000 psi in about 8.5 hours VHES-FRC with Fly Ash reached 3,000 psi in about 8 hours



All VHES-FRC systems had high cementitious content and high shrinkage values.



Main VHES factors to take into consideration: • • • • •

Low w/cm ratios Temperature range of the fresh concrete mixture: 85 ° F – 95 ° F Accelerating admixtures reduce set time and increase early strength gain Insulated curing Increased cement content

• Permeability of Cracked Fiber Reinforced Concrete • Preliminary Fiber Distribution Analysis 26

Permeability of Cracked Samples: Methods •

Splitting Tensile Test Setup and Magnifier with Scale

•

Relaxed Crack Widths Measured with Magnifier

0.1 mm

0.2 mm

0.3 mm

0.4 mm

0.5 mm 27

Permeability of Cracked Samples: Methods •

Saturation of Permeability Samples

•

Permeameter Apparatus (VTM – 120) and Permeability Testing Setup

28

Permeability of Cracked Samples: Results k=

k – coefficient of water permeability

Permeability Results

Coefficient of Water Permeability, k [cm/s]

0

100

200

300

400

500

600

1E-01 1E-02 1E-03 1E-04 1E-05 1E-06 Crack Width [µm] HES-FRC w/ S

Permeability Results

1E+00

HES-FRC w/ PP

700

0 Coefficient of Water Permeability, k [cm/s]

1E+00

ℎ𝑓𝑓 𝑎𝑎 ∙ 𝑙𝑙 ln( ) 𝐴𝐴 ∙ 𝑡𝑡 ℎ𝑜𝑜

100

200

300

400

500

600

1E-01

1E-02

1E-03

1E-04

1E-05

1E-06 Crack Width [µm] VHES-FRC w/ SF - S

VHES-FRC w/ SF - PP

VHES-FRC w/ FA - S

VHES-FRC w/ FA - PP

29

700

Fiber Distribution (Preliminary Analysis): Methods

30

Fiber Distribution (Preliminary Analysis): Results HD

TD

HD

TD

5.00

5.00

4.50

4.50

4.00

4.00

3.50

3.50

3.00

3.00

2.50

2.50

2.00

2.00

1.50

1.50

1.00

1.00

0.50

0.50

0.00

HD

TD

HD

TD

0.00 Horizontal Direction Cuts Number of Fibers / Unit Area

Transverse Direction Cuts

Horizontal Direction Cuts

Average Number of Fibers / Unit Area

Transverse Direction Cuts

Horizontal TD Direction Cuts

Number of Fibers / Unit Area

Horizontal Transverse Direction CutsDirection Cuts

Average Number of Fibers / Unit Area

31

Conclusions •

HES-FRC and VHES-FRC are promising technologies that may satisfy the accelerated construction and durability requirements. 

Accelerating admixture and increased fresh concrete temperatures (85 ° F – 95 ° F) enabled HES-FRCs to reach 3,000 psi in 24 hours.



For 3,000 psi VHES-FRCs to reduce the strength gain time to 10 hours:  The w/cm ratios were reduced,  Increased fresh concrete temperatures of 85 ° F – 95 ° F were used,  Increased amount and different types of accelerating admixtures were used,  Insulated curing was used,  Cement amount was increased.

•

The post-cracking flexural behavior was significantly enhanced. HES-ECC and FRCs w/ S fibers exhibited deflection hardening behavior.

•

Permeability increases with increase in crack width.

•

Fibers tend to align longitudinally along the length of the flexural beams.

32

Future Work •

Optimize HES-FRC mixtures for strength, shrinkage, and crack control, as well as make them more user friendly and cost effective.

•

Reduce shrinkage through mixture proportions and ingredients, including admixtures and lightweight aggregates.

•

Investigate if deflection hardening behavior is necessary when primary reinforcement is present.

33

Acknowledgements •

Virginia Transportation Research Council

•

University of Virginia

•

Federal Highway Administration

•

Virginia Department of Transportation

•

Industry

34

Thank you

Evelina Khakimova – [email protected] H. Celik Ozyildirim – [email protected] Devin K. Harris – [email protected]

Supplementary Slides

36

Stage I: HES-FRC

Fresh Concrete Properties

Compressive Strength - 3,000 psi in 24 hours HES-FRC w/ PP

HES-FRC w/ S

HES - ECC 15 lb/yd3

18 lb/yd3

HES- FRC w/ FA

HES-FRC w/ SF

2.5

5.3

5.3

5.5

5.2

-

8.5

4.75

7.5

4

Slump Flow [in]

20

-

-

-

-

Mix Temperature [ °F]

79

90

91

80

95

Air Temperature [ °F]

86

85

84

79

96

Air Content [%] Slump [in]

37

Testing

38



Equation below defines fresh concrete temperature T, where Ti is a temperature and Mi is the mass of mix components (Kosmatka, 2011)

𝑇𝑇 =

[0.22 ∙ 𝑇𝑇𝑎𝑎 ∙ 𝑀𝑀𝑎𝑎 +𝑇𝑇𝑠𝑠 ∙ 𝑀𝑀𝑠𝑠 +𝑇𝑇𝑐𝑐 ∙ 𝑀𝑀𝑐𝑐 + 𝑇𝑇𝑤𝑤 𝑀𝑀𝑤𝑤 + 𝑇𝑇𝑤𝑤𝑤𝑤 𝑀𝑀𝑤𝑤𝑤𝑤 + 𝑇𝑇𝑤𝑤𝑤𝑤 𝑀𝑀𝑤𝑤𝑤𝑤 ] [0.22 ∙ 𝑀𝑀𝑎𝑎 + 𝑀𝑀𝑠𝑠 + 𝑀𝑀𝑐𝑐 + 𝑀𝑀𝑤𝑤 + 𝑀𝑀𝑤𝑤𝑤𝑤 + 𝑀𝑀𝑤𝑤𝑤𝑤 ]

39

Stage I: HES-FRC

Temperature Development vs Age (HES-ECC) 200 180

Closure Pour 160

Temperature [°F]

•

Compressive Strength - 3,000 psi in 24 hours

140

Cylinder Field 120 100

Air Field

80

Cylinder Lab

Air Lab

60 40 0

5

10

15 Age [hours]

20

25

30

40